Technical field
The present inventions relate to electrical cable link apparatus and systems and particularly to the link boxes employed to implement earthing link and cross-bonding link.
Description of the Related Art
Link boxes are network components installed near HV (or MV or LV) cable joints and terminations and used to connect their screen conductors together through “cross-bonding” techniques. In particular, in a three-phase high voltage network line, the screens of each cable are cyclically connected such that the totally induced sheaths or screen current adds up to zero (e.g. vector currents) over the entire lengths of the line in order to minimize losses due to the axial induction currents in the metallic screen of each cable.
A typical link box comprises a metal box with a removable top cover and is provided by three lateral openings for screen cables entry, and an external earth connection. During installation, screen cables ends are firstly stripped of from the insulating sheath, inserted inside the lateral openings of the box, then fastened by means of screw terminals to the metal conductors implementing a specific connection scheme.
Document WO-01/73796 describes a three-phase high voltage cable arrangement having a cross-bonded cable screens and cross bonded water sensing wires. There are additional losses caused by the axial induction currents in the metallic screen of a cable. Such additional losses in the cable sheath, screen and other metallic system components can be reduced by grounding of the screens or metal sheaths at one end to avoid providing a closed loop for the induction currents, or by a so-called “cross-bonding” of the cable sheaths or screens to largely compensate the induction voltages such that the screen/sheath current and consequent losses are minimized in spite of the entire arrangement being grounded at both ends.